I offer three levels of book edits:

Developmental

Line or Copyediting

Proofreading

My only objective as the editor no matter which level is to make YOUR voice shine and produce a manuscript you will be proud of. I know a lot of editors are stiff grammarians, but I am not one of them. I am more concerned with my author's point of view and target reader than what a stylebook says. But I'm also quite fond of the Oxford comma and Chicago Manual of Style, just FYI! :) 

Editing should be a fun part of the journey. It should bring you joy to get one step closer to a finished product. I like to speak one-on-one with my authors at the beginning to make sure my vision is YOUR vision. I want to know your expectations so I can meet or exceed them.